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There are three major types of Blood flow Doppler patterns: 1) Continuous Wave 2) Pulse Wave 3) Color Flow DOPPLER ULTRASOUND

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What can We Measure with Doppler Ultrasound? Velocities: Most calculations start with this parameterVelocities: Most calculations start with this parameter Direction of Blood FlowDirection of Blood Flow Pressure GradientsPressure Gradients

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The Doppler Principle is the basis of many applications

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Beam alignment is crucial for accurate velocity measurements V = velocity of blood flow C = speed of sound in blood F T = transducer frequency F S = backscatter frequency Cos = cosine of angle between US beam & blood flow

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As the angle of the incident beam and the direction of blood increases the measured velocity decreases and the error increases DOPPLER BEAM BLOOD FLOW VELOCITY VECTOR MEASURED BLOOD FLOW VELOCITY VECTOR WHEN BEAM IS NOT PARALELL

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Effects of Intercept Angle in Velocity Measurements can not be ignored beyond 20 degrees

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Pulse Wave, Continuous Wave & Color Flow

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Color Flow Principle is similar to PW with multiple sector scans

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SPECIFIC APPLICATION OF DOPPLER MEASUREMENTS Pulsed Wave DopplerPulsed Wave Doppler –Stroke Volume Measurement Continuous Wave DopplerContinuous Wave Doppler –Peak velocity measurement Color DopplerColor Doppler –Blood Volume flow & direction

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Pulsed Wave Doppler Measures the blood velocity at a specific location or sample volume Exact localization of moving objects Limited maximum velocity measurement because of Nyquist Limit (more on this later)

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Pulsed Wave Doppler from transmittal flow to evaluate diastolic function

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Continuous Wave Doppler Measures the Maximum Velocity in a specific direction ( vs location for PW) Essentially no limit in the maximum velocity measurement (no Nyquist limit) The site of the maximum velocity cannot be localized

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Continuous Wave Doppler MR JET VELOCITY PROFILE DURING SYSTOLE, NOTE DIRECTION AND MAX VELOCITY

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Color Doppler Multiple sampling with pulsed wave Doppler along the 2D scan lines. The quantity and direction of velocity are measured in every point. The intensity of the signal represents number of moving cells Movement away from the transducer is blue and movement toward the transducer is red.

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Color Doppler Parasternal long axis (LAX )

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Blood Velocity Curves Can be measured any where there is flow and an Acoustic Window Basic calculus is used to analyze the velocity curves to obtain the Stroke Volume (SV) and Cardiac Output

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PW vs. CW thru the Mitral Valve

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Pulse Wave Thru Pulmonary Veins: Effects of Turbulence

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CONTINUOUS DOPPLER WAVES CAN BE USED TO MEASURE: STROKE VOLUME CARDIAC OUTPUT

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STOKE VOLUME WITH VELOCITY TIME INTERGRAL

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STROKE VOLUME & CARDIAC OUTPUT INTERGRAL OF BLOOD VELOCITY DISTANCE TRAVELED BY BLOOD AREA OF FLOW VOLUME OF BLOOD (STROKE VOLUME)

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Stroke Volume Measurement thru LV out flow tract (LVOT) SV = CSA LVOT x VTI LVOT SV = Stroke Volume CSA = Cross Sectional Area VTI = Velocity Time Integral LVOT = Left Ventricular Outflow Track

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Measuring Pressure Gradients

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Continuous Wave Doppler for Pressure Gradient Pressure Gradient = 4 x V 2 Pressure Gradient = 4 x V 2 1 – V 2 2 – Measuring maximum gradient through the narrowest area of the flow – Requires measuring the maximum velocity thru the area of flow with CW

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SUMMARY Doppler measurements have numerous applications in echocardiography. We can also measure the velocity of intra-cardiac structures (myocardium or valves) and assess their function or dysfunction.

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SUMMARY Understanding Echocardiography Physics will enhance our understanding of: The physical principles that affect our measurements and images Knowing when to believe or doubt our results The strengths and limitations of the technology

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